SYDNEY 
A group of radical anti-whaling activists said they were pelted with bloody chunks of whale meat and blubber after their boat collided Friday with a Japanese whaling vessel in a dramatic Antarctic Ocean clash Japan condemned as "unforgivable."

It was the second battle this week between the whalers and their foes. No one was injured, but the skirmishes mark the resumption of potentially life-threatening run-ins in a contentious fight that has become an annual fixture in the remote, icy and dangerous waters at the bottom of the world.

"The situation down here is getting very, very chaotic and very aggressive," activist Paul Watson, captain of the Sea Shepherd Conservation Society's vessel, told The Associated Press on Friday by satellite phone.

The clashes come as diplomatic efforts to resolve the controversy surrounding Japan's scientific whaling program appear to have stalled.

Japan – which has described the protesters as terrorists – plans to harvest up to 935 minke whales and 50 fin whales this season. Under International Whaling Commission rules, the mammals may be killed for research. Opponents say the Japanese research expeditions are simply a cover for commercial whaling, which was banned in 1986.

Watson said Friday's fracas began as his crew tried to maneuver their boat into a position that would have prevented the Japanese from dragging a whale on board their whaling vessel. Another Japanese ship shot in front of Watson's boat, causing a collision, Watson said.

"We can see the blood pouring out by the barrel," Watson said from his boat – named after the late Australian conservationist and TV personality Steve Irwin – as he watched the Japanese haul another whale onto their vessel. Earlier in the day, he said, the Japanese hurled pieces of blubber and whale meat at the Steve Irwin.

Japan blamed Sea Shepherd for the crash, characterizing the incident as a "deliberate ramming."

Shigeki Takaya, a Fisheries Agency spokesman for whaling in Japan, accused the conservationists of "appalling and unforgivable" acts.

"We will ask concerned countries, including Australia, to immediately stop them from carrying out such horrendous acts," Takaya said.

Protesters aboard the Steve Irwin set off from Australia in early December for the Antarctic Ocean, chasing the whaling fleet for about 2,000 miles (3,200 kilometers) before stopping two weeks ago in Tasmania to refuel. The group found the whalers again on Sunday and resumed their pursuit.

During the initial chase, Watson's crew pelted the Japanese with bottles of butyric acid, produced from rancid butter. In one December clash, Japan accused the Sea Shepherd crew of ramming one of its vessels, causing minor damage to the ship. Watson said the Steve Irwin only lightly brushed the whaling vessel.

This week, tensions escalated after Watson said two members of his crew were slightly injured when the Japanese blasted them with a water cannon and hurled heavy hunks of metal. Watson accused the Japanese of using a "military grade" noise weapon that can cause deafness and vomiting.

Despite the recent drama, this whaling season has been relatively peaceful compared to previous years.